This invention relates to a lightweight vacuum cleaner and in particular to a portable vacuum cleaner which is intended to be hand-carried as it sucks in dust through an inlet provided at its front end. Such lightweight vacuum cleaners will be referred to herein simply as portable vacuum cleaners, cordless or otherwise.
A portable vacuum cleaner according to a conventional design, as shown in FIG. 18, typically has a suction inlet 2 at the front edge of its housing 1 in such a way that its opening surface makes a rather large angle (.THETA. in FIG. 18) from the horizontal direction. When operating it, the user holds it by a handle 3 at the back and lifts its hind section as shown in FIG. 19, or causes it to stand on its front edge.
Since a vacuum cleaner of this type typically contains a dust collecting means such as a filter bag in front near the suction inlet 2 and an electric fan behind it, there is no problem as long as the fan is operating; but if the fan is stopped while the housing 1 is in the standing position, either for resting or for carrying the cleaner from one place to another, the dirt which has been accumulated inside the dust collecting means can easily fall out of the cleaner through the suction inlet 2. A method of preventing this is to provide a check valve made of a rubber sheet between the suction inlet 2 and the dust collecting means; but since this valve is operated by the motion of air caused by the electric fan, it is not effective against relatively heavy, small dust such as sand particles although large, light dust can be prevented from flowing backwards from the dust collecting means to the inlet 2.